page_title: Serial port
section_title: Hardware
hierarchical_section_title: Serial port / Hardware
caption_attribution_description: English: Virtual COM Port Hardware FTDI US-232R. FTDI US232R, see http://www.ftdichip.com/Products/Cables/USBRS232.htm
context_page_description: In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. Throughout most of the history of personal computers, data has been transferred through serial ports to devices such as modems, terminals, various peripherals, and directly between computers.
  While interfaces such as Ethernet, FireWire, and USB also send data as a serial stream, the term serial port usually denotes hardware compliant with RS-232 or a related standard, such as RS-485 or RS-422.
  Modern consumer PCs have largely replaced serial ports with higher-speed standards, primarily USB. However, serial ports are still frequently used in applications demanding simple, low-speed interfaces, such as industrial automation systems, scientific instruments, point of sale systems and some industrial and consumer products.
  Server computers may use a serial port as a control console for diagnostics, while networking hardware commonly use serial console ports for configuration, diagnostics, and emergency maintenance access.
context_section_description: Many historical uses of RS-232 may not meet the definition of a "serial port." While devices such as teletypes frequently used RS-232, in this context "serial port" refers to an interface to a computer.
  In the present day, many devices use an integrated circuit called a UART to implement a serial port. This IC converts characters to and from asynchronous serial form, implementing the timing and framing of data, and otherwise all the responsibilities of the serial protocol in hardware. The IBM PC implements its serial ports, when present, with one or more UARTs.
  Very low-cost systems, such as some early home computers, would instead use the CPU to send the data through an output pin, using the bit banging technique. These early home computers often had proprietary serial ports with pinouts and voltage levels incompatible with RS-232.
  Before large-scale integration (LSI) made UARTs common, serial ports were commonly used in mainframes and minicomputers, which would have multiple small-scale integrated circuits to implement shift registers, logic gates, counters, and all the other logic needed.
  On modern PCs, when a serial port is provided, it is commonly rolled in to the SuperIO chip.
caption: A converter from USB to an RS-232 compatible serial port; more than a physical transition, it requires a driver in the host system software and a built-in processor to emulate the functions of the IBM XT compatible serial port hardware.
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